1. Field of the Invention
This invention relates to treatment systems that treat municipal and industrial wastewater, raw water for a potable water supply, stormwater, urban runoff and combined sewer overflow (CSO), or any other flows of water having suspended particles. The inventive systems remove suspended particles from the water and, in particular applications for handling stormwater and CSO, retain and balance the flow to be treated.
2. Description of Related Art
Tanks for treating water to remove particles often utilize multiple parallel inclined plates with gaps between the plates that form passageways for the water to flow between the plates. The inclination of the plates creates a larger total horizontal projected settling area than a tank without inclined plates. This enlarged settling area increases particle settling ability in accordance with known surface load theories.
As the water flow passes through the gaps between the plates, particles settle out of the flow onto the surfaces of the inclined parallel plates. Because the plates are inclined to the horizontal, the particles move down the surfaces of the plates, off the ends of the plates, and down into a particle collection chamber below the plates. Over a period of time, some of the particles deposited on the surface of the inclined plates can accumulate to the point where the passageways between the plates become partially or completely clogged.
The treatment tank typically has an outlet channel having outlet openings or outlet weirs that allow a surface layer of water in the tank to overflow the outlet weir into the outlet channel to form an outflow. It is desirable to keep the "overflow" rate (the rate at which water is overflowing an outlet weir, per unit length of the outlet weir), to a relatively low rate to ensure that only a thin surface layer of water flows over the outlet weirs. The greater the overflow rate, the thicker the surface layer of water flowing over the outlet weir, and the more particles will be carried into the outflow.
Prior art treatment systems for handling stormwater, urban runoff, and combined sewer overflow mainly comprise retention tanks or tunnels dimensioned to collect and store a flow during and after a storm event, and devices for pumping the stored flow to existing treatment plants for treatment after termination of the storm event. Existing retention tanks and tunnels are not designed or equipped for treatment; they only function as storage tanks. Stored water is pumped from the retention tanks to existing or constructed sewage treatment plants after the storm events, for treatment.